1. Field of the Invention
The present invention relates to a camshaft for operating cylinder intake and exhaust poppet valves in an internal combustion engine.
2. Related Art
Contemporary internal combustion engines often include multiple camshafts. For example, V-type engines using overhead camshafts frequently include up to four such camshafts. Needless to say, the provision of multiple camshafts requires a good deal of machining in traditional engines because the camshafts are typically mounted upon towers which are cast into the engine cylinder heads, with each of the towers being first machined to accept a cap, which is constructed separately. The caps are applied to the towers and the tower and cap assembly is bored to allow mounting of a camshaft. The removable caps of such bearing towers are typically held in place by machine screws which must be properly torqued to provide an adequate bearing surface for the camshaft. Moreover, a tendency toward excessive tower porosity during the casting process makes the casting of cylinder heads with integral towers difficult. Another problem resides in the fact that bolted-on caps tend to distort the camshaft mounting bore, contributing to excess friction and in some cases, premature loss of engine oil pressure.
It would be desirable to provide a camshaft having completely unitary one-piece bearings held captive in an assembly, including a camshaft, which may be bolted to a cylinder head during an engine manufacturing process.